Manufacture of carbon black



June 2, 1931.

w. B WIEGAND MANUFACTURE OF CARBON BLACK Filed Feb. 18, 1929 2Sheets-Sheet l 'INVENTOR W17 @015. Wkyand BY "pm ATTORNEYS June 2, 1931.w. B. WIEGAND 1,307,884

MANUFACTURE OF CARBON BLACK Filed Feb. 18. 1929 2 Sheets-Sheet 2INVENTOR /fi mm; B, l Vl'cyarwl www- W ATTORNEYS 6 its properties invulcanized PateatedJ ne 2, 1931 UNITED STATES PATENT? OFFICEWILLIAMBRYAN 01 SOUTH BEACH, CONNECTICUT- mmrracruan or cannon BLACK.Applicatlon m February 18,- 1929. Serial no, 340,983.

My invention relates to im rovements in carbon black and in themanulPacture of-carbon black, and my invention includes a method ofimproving carbon black with respect to rubber compounds new carbon blackof special value in vulcanized rubber and a method of making these newcarbon black products. I

My invention relates particularly to car 10 bon black products producedby implngement of a hydrocarbon gas flame burning with the supply ofoxygen limited to permit only partial combustlon upon a cooler surfaceas in the well known and widely practiced channel rocess and the'term 1min ement car- P 9 p g black products bon black, when usedherein, ismtended to define carbon black products so produced and to distinguishsuch impingement carbon black products particularly from the softercarbon roduced by thermal decomposition of a hy rocarbon gas.

I have discovered that the impingement carbon blacks in vulcanizedrubber compounds can be-improved to a remarkable degree by calciningment carbon 1 'cination'nor do I now know '35 dation enables me to theimpingeack in a non-oxidizing atmosphere at temperaturesupwards of 1200F. I 0 not, at present, have any entirely satisfactory explanation ofthe result of the calexactly what changes occur during the calcination,but I do know that' calcinatlon at temperatures up-. wardsmf 1200 F.

while excluding air or causing or inducing oxi efiect an importantimprovement in the properties of impingement carbon blacks in vulcanizedrubber compounds. K,

Comparing impingement carbon blacks calcined in accordance with myinvention with the same carbon'blacks uncalcined, in vulcanized rubbercompounds, the improvements in tensile strength, in the modulus ofrigidity and in the energy'of resilience of the vulsteam or other mediaf canized rubber compound are particularly notable.v For example, 'isfrequently increased more and the modulus of ly increased as much as thetensile strength as muchas 50% or rigidity is frequentfor the rubbercompound calcined impingement carbon black. As comproperties of 100% ormore. The ageing properties of the vulcanlzed rubber aassusn to beimproved, as does the resistance of the vulcanized rubber compound towear and abrasion. Furthermore, rubber compounds including the improvedimpingement carbon blacks of my invention compound also seem jvulcanize.at a much higher rate than do the same compounds includin impingementcarbon black. l period of cure can, in man to one-half or one-third ofthe uncalcined or exam cases, be reduced the time required including theunpared to the usual carbon black products produced by thermaldecomposition, the improved impingement carbon' black products of myinvention are, moreover, blacker'in color.

I have just noted the improvements in v'ulcanized rubber compoundsincluding impingement carbon blacks made possible by my invention; Theimprovement in the properties of impingement carbon blacks made possibleby my invention are important in several other aspects. F example, myinvention makes it possible t treat impingement carbon blacks havingproperties in vulcanized rubber compounds too poor to be commercial-' 8,new source .wards of 1200 F: impingement carbon black of goodquality'with respect to its properties in vulcanized rubber compoundsbeforethis calcination, I can produce a new impingement carbon blackproduct superior-vnth respect to its properties invulcanized rubbercompounds, so far-as I amaware, to any'imple, the

t compounds. In this aspect, my invention makes available In anotherpmgement carbon black product heretofore known. I g

The new impingement carbon black products of my'invention can bedistinguished carbon black from the impingement carbon blacks heretoforeknown by comparison of the properties of the new carbon blacks and theknown carbon blacks in vulcanized rubber compounds. 5 In particular, ina standard rubber compoun the new impingement carbon blacks of myinvention will develop, on vulcanization, an unusually high tensilestrength and an unusually high modulus of rigidity. For the purpose ofcomparison the following standard compound may be used: 930 parts (byweight) of rubber (prime ribbed smoked sheets), 350 parts of carbonblack, 30 parts of zinc oxide, 50 parts of sulphur and 7.5 parts ofdiphenylguanidine; and this compound may be vulcanized in the usualplaten press (in a sheet iron frame 0.075 thick forming a slab 6 squarebetween plates of stainlesssteel 17 square and thick) at F. for 15minutes. The rime ribbed smoked sheets mentioned should be of a qualitydeveloping a tensile strength of about 3,300 pounds per square inch whenvulcanized in the usual platen press at 288 F. for forty .25 minutes inthis compound omitting carbon black. In this standard compoundvulcanized under these conditions, the new im pingement carbon blackproducts of my invention will develop a tensile strength-upwards of 4500pounds per square inch, as high as 4800 pounds per square inch orhigher, and a modulus of rigidity exceeding 1000, as high as 1200 orhigher. Such a tensile strength exceeds by hundreds of pounds and such amodulus of rigidity is within the neighborhood of twofold the values ofthese properties which can be obtained using the usual impingementcarbon blacks in this compound I vulcanized under these conditions. 4The new impingement carbon black products of my invention can also bedistinguished from the impingement carbon blacks heretofore known by thephysical properties of the new carbon black itself. They may, ample, bedistinguished by capacity, or rather their lack of absorptive capacity,and their volatile content; The new impingement carbon black products ofmy invention have a volatile content, by the for extheir absorptiveBureau of Mines coal analysis method (see Bureau ofMines Techni'calPaper7 6 and J ournal of Industrial and Engineering Chemistry, volume 9,1917, page 102), of not more than about 4%. Likewise, the newimpingement roducts of my invention have a characteristically lowabsorptive capacity with respect to organic accelerators of V111.canization such as diphenylguanidine; testing a 1 gram sample of thecarbon black in 3 50 cc. of a solution of diphenylguamdinein ethylalcohol containing 2 grams of diphenylguanidine per liter,

the new carbon black products of my invention will remove from thesolution not more than about 6% of the total diphenylguanidine present.

d of the black decrease;

'an impingement I have observed that pingement carbon blacks invulcanized rubber compounds improve as the volatile content of the blackand the absorptive capacity that is the impingement carbon blacks of thelower volatile content and the less absorptive impingement carbon blacksseem to have better properties in vulcanized rubber compounds. Ingeneral, impingementcarbon blacks having a volatile content of not morethan about 7.5% and an absorptive. of not more than about 11%, in termsof the tests mentioned above, have satisfactory properties in vulcanizedrubber compounds. v

I have noted that the new pingement carbon black products of myinvention have particularly low volatile content and absorptivecapacity, but in another aspect my invention provides a method ofreducing the volatile content and absorptive capacity of carbon blacksgenerally and thus improving their properties in vulcanized rubber,compounds. For example, it is possible, by means of my invention, toreduce the volatile content of carbon black from, say, 29-10% to 67% aswell as to reduce the volatile content of an impingement carbon blackfrom, say, 56% to 3-4%and' to reduce the absorptive capacity of animpingement carbon black from, say, 1112% to 8-9% as well as to reducethe absorptive capacity of an impingement carbon black from, say, 810%to 5-6%, in terms of the tests mentioned above.

Continued or repeated application of the caloination treatment of myinvention, however, apparently does not continue to improve impingementcarbon black with respect to its roperties in vulcanized rubbercompounds.

Up to a limited total period of treatment, the

of my invention continues to improve the lack, but beyond this limitthere seems-to be no further improvement. However, the improvementeffected up to this limit seems to e retained, at least in lar e part,even though the period ment e much prolonged. In other words, to

secure best results .the caloination must be continued for a certainminimum period of time but it is not important if the caloination iscontinued for a longer period of time.

Within limits, the time and temperature of the caloination seem to besomewhat inter-related, a longer period'of treatment being requiredatlower temperature than at higher temperature. For example, in treatingthe usual impingement carbon blacks, marked improvement of the carbonblack with respect to its'pro erties' in vulcanized rubber compounds iseveloped by caloination for periods of 7-10 minutes at temperaturesapproximating 13501400 vI -while at 1250 F. the caloination might haveto be continued for a period of as much as 20 minutes the properties ofimof treat- I rubb or more to effect a comparable improvement in thesame carbonblack. It is thus advantageous to carry out the calcinationat temperatures upward of 1300 F. A period of calcination upwards of 5minutes, at temperatures of 1200-1300 F is usually required to developthe maximum improvement in the properties of the carbon black invulcanized rubber compounds. The period of calcination may be regulatedwith respect to the improvement effected. ,Marked improvement ofimpingement carbon blacks with respect to their properties in vulcanizeder compounds is usually effected when, by the calcination treatment ofmy invention, the volatile content of the carbon black has beendecreased not less than 1% and the absorptive capacity of the carbonblack has been decreased by a margin of not less than 2%, in terms ofthetests mentioned above. The calcination treatment of my invention is,with advantage, continued until the carbon black has a volatile contentless by at least 1% and an absorptive capacity less by at least 2%, interms of the tests mentioned above,

than the uncalcined carbon blac in the accompanying I havejust notedthat continued or repeated appllcatlon of the calcination treatment ofmy invention apparently does not continue to improve impingement carbonblack with respect to its properties in vulcanized rubber compounds, andthis makes it possible to dis tinguish the resultant improved carbonblack product produced by calcination of a low quality impingementcarbon black in accordance with my invention from an uncalcinedimpingement. carbon black of satisfactory quality even though the lattermay have prop erties in vulcanized rubber compounds comparable to thoseof the calcined impingement carbon black, initially of low quality butbrought to satisfactory quality by calcination. In this aspect my'invention provides a new impingement carbon black product having avolatile content of not more than 7.5%

and an absorptive capacity of not more than Wh 11%, in terms of thetests mentioned above, which volatile content and absorptive capacityare not substantial-1y decreased by calcination, say, at 1300 F. for aperiod of 10 minutes in a non-oxidizing atmosphere.

I have carried out my invention on a commercial scale in apparatus ofthe type illustrated, diagrammatically andconventionally, drawings. Inthese drawings, Fig. 1 is a fragmentary elevation, partly in section, ofone form of apparatus adapted for carrying out my invention and Fig. 2is another fragmentary elevation, partly in section, of the sameapparatus, normal to Fig. 1.

The apparatus illustrated comprises a supply receptacle 1 connected tothe upper end of a group of calcining tubes 2 extending through afurnace 3 in turn connected through provided for the introduction of aseries of cooling tubes 4 to a discharge conveyor 5. The calciningfurnace 3 is of brick supported upon a number of steel channels 6 inturn carried by a concrete foundation 7. At each end of the furnace 3apertures 8 are gas burners; the two lower pairs are usually suflicicut.The Waste heating gases escape through stack flue 9. An agitator 10extends through each of the calcining tubes 2 and through the supplyreceptacle 1 above the calcining tubes. Each of these agitators iscarried by a pair of bearings 11 and 12 arranged above the supplyreceptacle 1. Elevator-conveyor '13 is provided for supplying'rawimpingement carbon black to the supply receptacle 1. Screw conveyors 14are provided for carrying'calcined carbon black through the coolingtubes 4;. A screw conveyor 15 is provided for discharging the cooledcalcined carbon black through the conveyor 5. Connection 16 is providedfor taking samples. 7

have carried out my invention on a commercial scale in apparatus of thetype illustrated in which the supply receptacle 1 is 17" wide, 55 longand 60 deep, exclusive of the hopper bottom, the latter being 9 deep, inwhich the calcining tubes 2 comprise six tubes 4 in inside diameter and48 long within the furnace, and in which the cooling tubes 4 comprisesix tubes 4 in inside diameter and about 60 long. In such an apparatusas much as 1000 pounds per day of impingement carbon black can besubjected to calcination, in accordance with my invention, fora periodof 10 minutes.

In carrying out my invention in apparatus ofthe type illustrated, rawimpingementcarbon black is dumped into the supply receptacle 1 by meansof elevator-conveyor 13 until the tubes 2 are full of the black, untilthe bottom of the supply receptacle 1 is completely covered with black,and until the su ply receptacle 1 is partly filled with blach. The firesare then started in thefurnace 3. en the furnace temperature reaches13001350 F., or shortly before that time, the

, agitators 10 and the screw conveyors 14 are by means ofelevator-conveyor 13. The passage of the black through the calciningtubes is relatively slow so that the black in passing through thecalcining tubes, being at the same time agitated, is brought to atemperature closely approximating the furnace temperature itself. Thebottom of the supply receptacle 1 being exposed to the heating gases,the black is preheated within the supply receptacle itself. As the blackis heated in the calcining tubes, gases are driven off and these 5. Animpingement carbon black product gases, through'the action of theagitators 10, having a volatile content of not more than escape easilythrough the tubes and the charge 4% and of which a 1 gram sample willabsorb of black maintained in the supply receptacle from50 cubiccentimeters of an alcoholic so- 5 l. Access'of air to the black withinthe callution of diphenylguanidine containing 2 cining tubes isprevented by maintaining the grams per liter not more than 6% of thetotal supply receptacle 1 partially r'ull of black diphenylguanidinepresen and by maintaining the cooling tubes 4, and 6. An impingementcarbon black product also the dead ends 17 of these cooling tubes,which, in a rubber compound consisting of full of the calcined black, asthe operation 930 parts of rubber prime smoked sheets) \75 rocecds.These precautions, in connection 350 parts of the car on black, parts 0with the pressure of the gases formed within zinc oxide, parts ofsulphur and 7.5 parts the calcining tubes, effectively maintain a ofdiphenylguanidine vulcanized at 288 F.

non-oxidizing atmosphere within the calcinfor 15 minutes, will develop atensile strength 15 ing tubes. The cooled calcined black is disexceeding4500 pounds per square inch and charged through conveyor 5 to bolters. amodulus of rigidity exceeding 1000.

The cooling tubes 4, instead of being cooled 7. An impingement carbonblack product by air, may be arranged within a water tank having avolatile content of not more than to provide more eiiective cooling. Thecool- 7.5% and of which a 1 gram sample will ab- '20 mg tubes 4, forexample, may be vertically arsorb from 50 cubic centimeters of analcoholic ranged as extensions-of the calcining tubes 2 solution ofdiphenylguanidine containing extending through a water tank' arrangedbegrams per liter not more than 11% of the neath the furnace. totaldiphenylguanidine present and of It is intended and will be understoodthat which the volatile content and the absorptive 25 the foregoing moredetailed description of capacity for diphenylguanidine, measured onemethod of carrying out my invention in by this test, are notsubstantially decreased connection with the particular apparatus ilbycalcination at 1300 for a period of 10 lustrated in the accompanyingdrawings is minutes in a non-oxidizing atmosphere.

merely for the purpose of exe" plification. 8. An impingement carbonblack product 30 My invention can be practiced in other and produced bycalcining impingement carbon different apparatus and in apparatus ofdiiblack at a temperature not less than about ferent size. 1200 F. in anon-oxidizing atmosphere.

I claim? 9. An impingement carbon black product 7 1. A method ofimproving the properties produced by calcining impingement carbon 35 ofimpingement carbon blacks in vulcanized black at a temperature not lessthan about rubber compounds which comprises calcin- 1300 F. inanon-oxidizing atmosphere.

ing the impingement carbon black at a tem- 10. An impingement carbonblack product perature not less than about 1200 F. in a nonproduced bycalcining impingement carbon oxidizing atmosphere. black at atemperature not less than about 40 2. A method of improving theproperties 1200 F. for a period not less than about five of impingementcarbon blacks in vulcanized minutes in a non-oxidizing atmosphere.rubber compounds which comprises calcin- In testimony whereof I afiix msignature. ing the impingement carbon black at a tem WILLIAM BRYAN WIGAND. perature not less than about 1300 F. in a 4 non-oxidizingatmosphere. no

3. A method of improving the properties of impingement carbon blacks invulcanized rubber compounds which comprises calcining the impingementcarbon black at a tem perature not less than about 1200 F. for a n5 55rubber compounds which comprises calcining period upwards of 5 minutesin. a non-oxidizing atmosphere.

1. A method of improving the properties of impingement carbon blacks invulcanized the impingement carbon black at a tempera ture upwards of1200 F. until the volatile content of the black is decreased not lessthan 1% and until a 1 gram sam le of the calcined 60 black will absorbfrom 50 cu ic centimeters of an alcoholic solution of diphenylguanidinecontaining 2 grams per liter a percentage 0 the total diphenylguanidinepresent less by a margin of not less than 2% than a 1 gram 65 sample ofthe uncalcined black.

